Thin-window recording tube

ABSTRACT

A faceplate of a thin-window recording tube comprising a metal backing electrically isolated from the outside of an evacuated envelope of the recording tube. An embodiment of the faceplate has a metallic support the side surfaces of which are covered with an insulating adhesive. Another embodiment has a metallic support the elongated target of which has formed therein a plurality of circular apertures.

United States Patent Miyama et al.

[451 Apr. 18, 1972 154] THIN-WINDOW RECORDING'TUBE [72] Inventors: lllroshi Miyama; Kaoru Tomii, both of Osaka, Japan [73} Assignee: Matsushita Electric industrial Company,

Limited, Osaka, Japan [22] Filed: Nov. 18, 1970 [21]- Appl. No.: 90,734

[30] Foreign Application Priority Data I 1 Nov. 19, 1969 Japan ..44/11042s Nov. 25, 1969 Japan ..44/94803 [52] U.S.Cl. ..313/92 R,313/74 [51] lnt.Cl ..ll01j 29/18, HOlj 29/28,HOlj33/00 [58] Field of Search ..313/92, 74

[56] References Cited UNITED STATES PATENTS 3/1935 Knoll ..3l3/92 X 2,263,733 11/1941 Knoll ..313l92 X 2,251,332 8/1941 Gray.... 3,157,879 1l/1964 Kuehler ..3 13/74 X.

FOREIGN PATENTS OR APPLICATIONS 1,159,288 7/1969 Great Britain ..313/92 Primary Examiner-Robert Segal Azt0rney.lohn Lezdey [57] ABSTRACT A faceplate of a thin-window recording tube comprising a metal backing electrically isolated from the outside of an evacuated envelope of the recording tube. An embodiment of the faceplate has a metallic support the side surfaces of which are covered with an insulating adhesive. Another embodiment has a metallic support the elongated target of which has formed therein a plurality of circular apertures.

2 Claims, 5 Drawing Figures THIN-WINDOW RECORDING TUBE This invention relates to a thin-window recording tube and more particularly to a faceplate having a metal backing electrically isolated from the outside of an evacuated envelope of the recording tube.

A conventional recording tube has a metal backing deposited on its fluorescent layer. The metal backing is scanned by an electron beam for transmitting therethrough the electron beam to the fluorescent layer to cause an optical signal to be produced in the fluorescent layer in accordance with an electric signal borne by the electron beam. The metal backing is electrically connected through a metallic support to the outside of an evacuated envelope of the recording tube. A high positive potential is usually applied to the metal backing. This incurs a serious danger to the operator when in operation.

The conventional recording tube also uses a metallic support secured to a thin transparent sheet and having a slit aperture acting as a target for an electron beam. The width of .the slit aperture should be small enough to assure sufficient mechanical strength of the transparent sheet which is subject to a high pressure difference between the inside and outside of the evacuated envelope. The aperture, thus, being extremely narrowed, it is difficult to uniformly fit the fluorescent layer into such narrow aperture and to deposit the metal backing on the fluorescent layer. It is also difficult to enable the electron beam to precisely scan the narrow target so as to prevent the electron beam from missing the target. i

It is, therefore, an object of this invention to provide an improved faceplate having a metal backing electrically isolated from the outside of an evacuated envelope of a recording tube.

It is another object of the invention to provide an improved faceplate having an elongated target which is composed of a plurality of circular apertures formed therein.

In the drawings:

FIG. 1 is a cross-sectional view showing a preferred embodiment of a faceplate according to this invention;

FIG. 2 is similar to FIG. 1 but shows another preferred embodiment of the invention;

FIG. 3 is an enlarged top view of a portion of a faceplate shown in FIG. 2;

FIG. 4 is a sectional view taken along the line 4-4' of FIG. 3; and

FIG. 5 is similar to FIG. 4 but is taken along the line 5-5 of FIG. 3.

Referring now to FIG. 1, there is shown a faceplate according to this invention, which is generally indicated at numeral 10. The faceplate comprises a transparent sheet 11 and a metallic support 12 both having a similar coefficient of thermal expansion. The transparent sheet 11 is made of a rigid transparent material such as glass or mica and has substantially the same area as that of the end surface of an evacuated envelope 13 of a recording tube. The metallic support 12 has substantially centrally thereof an elongated target of a slit aperture and is narrower than that of the end surface of the envelope 13. The metallic support 12 is secured to the transparent sheet 11 in alignment therewith to form a junction. A fluorescent material is fit into the slit target and is deposited thereon to form a fluorescent layer 14. The fluorescent layer 14 is coated with a metal backing 15 by vacuum evaporation. The junction, which is made up of the fluorescent layer 14 and the metal backing 15 in its slit target, is secured to the end of the evacuated envelope 13 by an adhesive 16 with its metallic support 12 facing an electron gun (not shown) of the recording tube. In this instance, the adhesive 16 may preferably be of electrically insulating property and may cover not only the inner surface of the metallic support 12 but the side surfaces of the same. Since the metallic support 12 is closely received by the insulating adhesive 16 in such a manner as described above, the metal backing 15 is electrically insulated'from the outside ofthe evacuated envelope 13. I

When, in operation, an electron beam emitted from the electron gun and indicated at numeral 17 hits lengthwise the metal backing 15 of the slit target, a substantial portion of the electron beam 17 transmits therethrough and causes the fluorescent layer 14 to luminesce in accordance with the electric signal supplied to the electron gun. The metal backing I5 and accordingly the metallic support 12 are biased with a high positive voltage, but, because the metallic support 12 is enclosed with the insulating adhesive 16, there is the operator can be freed of a danger even when the touches the outside of the envelope l3. 1

FIGS. 2 to 5 show a more preferre'd embodiment of, a faceplate according to this invention, in which similar numerals indicate corresponding elements of the faceplate.

As best shown in FIGS. 3 to 5, the faceplate, generally indicated at numeral 20, comprises a junction including a transparent sheet 11' and a coextensive metallic support 12' secured by fusion to each other. The metallic support 12' has substantially centrally thereof an elongated target composed of a plurality of circular apertures. The circular apertures may preferably be arranged in an array and have diameters smaller than that of the electron beam 17. To the contrary of the first embodiment, the fluorescent layer 14' is directly deposited on the surface of the transparent sheet 11' opposite to the metallic support 12'. It is quite natural that the fluorescent layer 14' be positioned coextensively with the elongated target. The fluorescent layer 14 is also covered with a metal backing 15'. The junction is secured by an adhesive 16' to the end of the evacuated envelope 13 with its transparent support 12' facing the electron gun. In this instance, the adhesive 16' need not be of insulating property because the metal backing 15' is electrically isolated by the transparent insulating sheet 11 from the outside of the envelope 13. As shown, it is of no importance whether or not the adhesive 16 does enclose the transparent sheet 11'.

The faceplate of the latter embodiment is advantageous in the following respects: It is easy to manufacture because the fluorescent layer and the metal backing can be directly ap plied on the surface of the transparent. sheet without fitting them into an extremely narrow target. With a plurality of circular apertures provided, the effective width of the target is increased without sacrificing the mechanical strength of the faceplate itself. In addition, a higher resolution is available because a plurality of convex lenses are formed of those portions of the transparent material which are raised into the corresponding circular apertures, as shown, when the transparent sheet is fused to the metallic support.

What is claimed is:

l. A faceplate for a thin-window recording tube having an evacuated envelope and an electron gun, said evacuated envelope having an elongated aperture formed at the end opposite to said electron gun, said faceplate comprising:

a junction having a transparent sheet and a metallic support which are secured to each other and have a substantially common coefficient of thermal expansion, said metallic support having a plurality of circular apertures formed to provide a thin window which extends lengthwise and substantially centrally of said metallic support, said transparent sheet being fused to said metallic support so that convex lenses are formed of those portions of said transparent sheet into said apertures,

a fluorescent layer deposited on said transparent sheet coextensively with said thin window,

a metal backing deposited on said fluorescent layer, and,

an insulating layer acting as an adhesive agent to mount said junction on the end of said evacuated envelope with said transparent sheet in contact with said insulating layer, whereby an electron beam emitted from the electron gun and then passing through the elongated aperture scans said metal backing lengthwise, causing said fluorescent layer to luminesce in accordance with an electric signal supplied to the electron gun,

said metal backing being electrically isolated from outside of said evacuated envelope.

2. A faceplate according to claim 1 wherein said circular apertures are in an array and have diameters smaller than that of said electron beam. 

1. A faceplate for a thin-window recording tube having an evacuated envelope and an electron gun, said evacuated envelope having an elongated Aperture formed at the end opposite to said electron gun, said faceplate comprising: a junction having a transparent sheet and a metallic support which are secured to each other and have a substantially common coefficient of thermal expansion, said metallic support having a plurality of circular apertures formed to provide a thin window which extends lengthwise and substantially centrally of said metallic support, said transparent sheet being fused to said metallic support so that convex lenses are formed of those portions of said transparent sheet into said apertures, a fluorescent layer deposited on said transparent sheet coextensively with said thin window, a metal backing deposited on said fluorescent layer, and, an insulating layer acting as an adhesive agent to mount said junction on the end of said evacuated envelope with said transparent sheet in contact with said insulating layer, whereby an electron beam emitted from the electron gun and then passing through the elongated aperture scans said metal backing lengthwise, causing said fluorescent layer to luminesce in accordance with an electric signal supplied to the electron gun, said metal backing being electrically isolated from outside of said evacuated envelope.
 2. A faceplate according to claim 1 wherein said circular apertures are in an array and have diameters smaller than that of said electron beam. 